Tobacco smoke filter material

ABSTRACT

An improved cigarette filter material is formed from the porous, granular salt of a weakly basic anion exchange resin, said salt being formed by the at least partial neutralization of the basic resin by a weak acid. The salt is characterized by a surface area of from about 1 to 100 square meters per gram, a pore volume of from 0.2 to 0.5 cubic centimeters per gram, an average pore diameter of from about 0.1 to 1.0 microns and the salt is formed by the at least partial neutralization of the basic resin by a weak acid having a pKa between 3.5 and 5.5.

States atent 91 laitzinger [11] 3,828,800 1451 Aug. 13, 1974 TOBACCOSMOKE FILTER MATERIAL [75] Inventor: Elmer Francis Litzinger,Louisville,

[22] Filed: Sept. 11, 1972 [21] Appl. No.: 287,633

Related [1.8. Application Data [62] Division of Ser. No. 75,772, Sept.25, 1970.

52 us. cl. 131/262 [51] int. Cl. A24f 7/04 [58] Field of Search 131/10,177

[56] References Cited UNITED STATES PATENTS 2,881,772 2/1959 Touey et a1222/177 3,280,823 12/1966 Bavley et a1. 131/10 Primary Examiner-MelvinD. Bein Assistant Examiner-Vincent Millin Attorney, Agent, orFirm-Finnegan, Henderson, F arabow & Garrett [5 7] ABSTRACT An improvedcigarette filter material is formed from the porous, granular salt of aweakly basic anion exchange resin, said salt being formed by the atleast partial neutralization of the basic resin by a weak acid. The saltis characterized by a surface area of from about 1 to 100 square metersper gram, a pore volume of from 0.2 to 0.5 cubic centimeters per gram,an average pore diameter of from about 0.1 to 1.0 microns and the saltis formed by the at least partial neutralization of the basic resin by aweak acid having a pKa between 3.5 and 5.5.

5 Claims, No Drawings 1 TOBACCO SMOKE FILTER MATERIAL This is a divisionof application Ser. No. 75,772, filed Sept. 25, 1970, now U.S. Pat. No.3,716,500.

BACKGROUND OF THE INVENTION Hitherto it has been proposed to employ incigarette filters ion exchange resins for the purpose of removingvarious constituents from tobacco smoke, particularly nicotine, acids,and tar. Specifically, cation exchange resins have been proposed fornicotine removal and anion exchange resins for the removal of smokeacids.

' Strongly basic anion exchangers proposed for the latter SUMMARY OF THEINVENTION It is, therefore, an object of the present invention toovercome the difficulties and disadvantages heretofore encountered andto provide an improved filter material for delivering to the mouth ofthe smoker a smoke stream of the desired composition having the desiredorganoleptic characteristics and from which selected volatile componentshave been removed while leaving in the smoke, or returning or deliveringthereto, desired flavor and aroma imparting materials.

The above and other beneficial objects and advantages are obtained inaccordance with the present invention by an improved tobacco smokefilter material comprising the porous, particulate salt of a weaklybasic anion exchange resin, said salt being formed by the at leastpartial neutralization of the basic resin by a weak acid. It has beenfound that weakly basic anion exchange resins, particularly those with asignificant proportion of primary amine groups, selectively removetobacco smoke carbonyl compounds. The reaction is catalyzed by weakacids, and the utilization of the above anion exchange resins as saltsof weak acids provides highly efficient filter material for theselective removal of volatile aldehydes, such as acetaldehyde andacrolein, from cigarette smoke while maintaining the capacity of theresin for filtering other components, such as hydrogen cyanide.

Enhanced selective filtration is obtained by employing a highly porousgranular resin for exposing the active chemical functionality to thesmoke stream.

The term pK,," as employed hereinbelow designates the first ionizationconstant of the weak acid used to convert the basic anion exchange resin(in free base form) to its salt form.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The anion exchange resin matrixof the weakly basic resin may be of the conventional polystyrene,styrenedivinylbenzene, phenolic, acrylic or aliphatic types. A preferredresin matrix is a phenol formaldehyde condensate.

The weakly basic resin may be formed by combining, using conventionalmeans, a polyamine with the previously described resin matrix.Substantial improvement is obtained in the selective filtrationproperties of the material when the weakly basic anionic exchange resincontains at least about 30% free primary amino groups prior to reactionwith a weak acid in accordance with the invention.

Examples of typical polyamines include: ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,propylenediamine, metaphenylenediamine and the like.

It is of critical importance that the weakly basic anion exchange resinbe formed from porous and preferably granular particles, rather thanconventional smooth, nonporous spherical resinous particles.

For best results the porous, granular resin particles are formed with asurface area of from about 1 to 100 square meters per gram. The porevolume of the granules is preferably from about 0.2 to 0.5 cubiccentimeters per gram. The average pore diameter (assuming cylindricalpores) of the resin granules is preferably from about 0.01 to 1 micron.

Particularly preferred weakly basic anionic exchange resins capable ofbeing at least partially neutralized by the weak acids of the inventionare the porous, granular phenol-formaldehyde-polyamine terpolymerresins, designated Duolite A-2 and Duolite A-7 and distributed byDiamond Shamrock Chemical Company. The following table sets forth thephysical characteristics of the A-2 and A-7 resins. In the table thesurface area is expressed in terms of square meters per gram, the porevolume in cubic centimeters per gram, and the pore diameter in microns.

Physical Properties of Preferred Porous Ion Exchange Resins Pore DuoliteA-7 The filter material of the invention is formed by neutralizing allor a portion of an aforementioned basic resin with a weak acid. Resinsalts derived from acids conventionally designated as strong acids andfrom acids conventionally designated as very weak" acids are generallynot effective in removing volatile aldehydic components of tobaccosmoke. In general, acids having a pK below about 3.5 or above about 5.5yield unsatisfactory reductions of aldehydic components. For bestresults and markedly superior aldehyde removal, acids having a pK offrom about 4 to 5 are employed.

Preferred weak acids include aromatic and aliphatic carboxylic acidshaving a pK of from about 4 to 5 and include such aromatic carboxylicacids as benzoic acid, cinnamic acid and anisic acid and such aliphaticdicarboxylic acids as succinic acid and glutaric acid.

Further enhanced results are obtained and accordingly it is particularlypreferred to employ aliphatic monocarboxylic acids, including thefollowing: propionic acid, valeric acid, caproic acid, heptanoic acid,caprylic acid, and pelargonic acid.

Especially preferred weak acids which have proved to be most efficientin removing volatile components from tobacco smoke when combined withthe above basic anion exchange resins are acetic acid and glutamic acid.Additional enhancement is obtained when the free basic resins derivedfrom phenol-formaldehyde-polyamine terpolymers such as the Duolite A-2and A-7 resins, are fully or partially neutralized by either acetic acidor glutamic acid.

By completely neutralizing the free base form of the resins of theinvention with the weak acids of the invention, significant reductionsof volatile components such as hydrogen cyanide, acetaldehyde andacrolein are achieved. In the case of the Duolite A-2 and A-7 resinsneutralized with acetic acid or glutamic acid increased reductions offrom 30 to 35 percent acetaldehyde and from to percent acrolein havebeen obtained based on reductions achieved by the free base resin priorto neutralization.

Even partial neutralization of the free base resin significantly reducesthe quantity of volatile aldehydic compounds in tobacco smoke ascompared to the quantity removed by the free base resins and alsosubstantially reduces the ammoniacal odor often associated with the freebase (amine-type) resins. The efficiency of a tobacco smoke filteremploying material of the invention can be increased as to removal ofvolatile components and, particularly, the aforementioned aldehydes, bymore completely neutralizing the free base resin and/or by employinglarger quantities of the at least partially neutralized resin in thefilter.

In general, sufficient quantities of the filter material of theinvention are employed to significantly reduce the quantity of undesiredvolatile components normally present in tobacco smoke and, particularly,hydrogen cyanide, acetaldehyde, and acrolein. For this and otherpurposes it is preferred to employ from about 50 to 150 milligrams ofthe filter material in a filter for use in smoking articles such ascigarettes.

In one embodiment, a filter is prepared by encasing the filter materialin an outer wrapper. The resulting filter may be employed alone or incombination with conventional cellulose acetate filters. Triple filtersemploying sequentially, the following filter sections cellulose acetate,the filter material of the invention, and cellulose acetate, have provenparticularly workable. The filter material may be used in conjunctionwith perforated cigarette paper, if desired, or filter ventilation meansmay be employed. In another embodiment the filter material may bedispersed, in granular form, either on paper or on cellulose acetate towand encased in an outer wrapper.

The following examples are provided to further illustrate the nature ofthe invention and are not [imitative of scope.

EXAMPLE I In order to illustrate the effectiveness of the filtermaterial of the invention certain salt and free base forms of twodifferent phenolformaldehyde-polyamine terpolymer resins were formedinto filters for cigarettes.

Filter materials of the invention were formed from thephenol-formaldehyde-polyamine terpolymer resins identified as DuoliteA-2 and Duolite A-7 anion exchange resins, distributed by the DiamondShamrock Chemical Company. The resins are commercially obtainable in theform of a chloride-sulfate mixed salt. For test purposes portions of themixed chloride-sulfate salt of the A-2 and A-7 resins were converted tothe free base resin. Portions of the free base resin were converted tothe acetate or glutamate salt by complete neutralization with aceticacid or glutamic acid.

The neutralization capacities of the A-2 and A-7 resins are ca. 5.0milliequivalents of weak acid per gram of resin. Predeterminedquantities of the resin derivatives were packed into 7 millimetercavities between 7 millimeter lengths of conventional cellulose acetatefilters of 84 millimeter cigarettes, (tobacco sections 63 millimeters inlength). The resulting cigarettes were smoked to 28 millimeter buttlengths on a constant vacuum smoking machine taking 35 milliliter puffsof 2 seconds duration at one minute intervals.

In the following table the weight of the filter material is expressed inmilligrams. The filter efficiency represents the weight per cent ofcomponent trapped by the filter material based on the total amount ofthe component passing through the cigarette filter.

SELECTIVE FILTRATION EFFICIENCIES Resin Form Resin Hydrogen Acetal-Acro- Weight Cyanide dehyde lein Duolite Unmodified I30 27 3 l9 A-2(chloride sulfate salt) Free base 120 82 49 52 Acetate salt 120 80 79 72Glutamate salt I40 84 75 71 Duolite Unmodified I45 49 O 35 A-7(chloridesulfate Salt) Free base I25 8! 31 56 Acetate salt 140 66 70 Thefree base resin forms exuded a perceptible ammoniacal odor. This odorwas eliminated by the formation of the acetate and glutamate salts ofthe above resins. The above table illustrates the significantenhancement in removal of volatile components, particularly aldehydiccomponents, from tobacco smoke obtained by employing the filtermaterials of the invention. Similar results are obtained when otherweakly basic anion exchange resins, at least partially neutralized withweak acids, are employed.

In the following table any of the resin matrixes may be combined withany of the polyamines to form the weakly basic exchange resin of theinvention and such resins may be at least partially neutralized with anyof the following weak acids:

EXAMPLE II In order to illustrate the enhanced selective filtrationresults obtained in employing the weak acid salts of the weakly basicanion exchange resins, the phenol-formaldehyde-polyamine terpolymerresin (designated Duolite A-2 resin) of Example I was completely neu-Effect of pK of Weak Acid on Selective Filtration Efficiency As shown bythe foregoing table strong and very weak acid salts are ineffective inremoving volatile components such as aldehydes from tobacco smoke. Weakacids, particularly those having a pK in the range of from about 4 to 5,show significantly enhanced selective filtration properties. This effectis dramatized by comparing the filtration efficiencies of the oxalatesalt with the succinate salt. While both acids form dicarboxylate resinsalts, nevertheless, the succinate salt (pK,,-succinic acid 4.16)exhibits a marked improvement in removal of aldehydes from tobacco smokeas compared with the oxalate salt (pK -oxalic acid 1.23).

EXAMPLE lll The effect of the physical properties of the resin salts onselective filtration are demonstrated in the following Example. With theexception of the Duolite A-7 acetate resin, the acetate salts of theweakly basic anion exchange resins set forth in the following table wereemployed in the form of smooth, non-porousbeads. The resins were formedinto filters and tested and reported in accordance with procedures inExample l.

The Dowex-3 resin is a styrene-divinylbenzene polyamine resin. AmberliteIR-4B is a phenol-formaldehyde polyamine resin. Permutit de-Acidite isan aliphatic polyamine resin. The resins were fully neutralized to theacetate salt.

Effect of Physical Properties of Resin on Selective FiltrationFiltration Efficiencies Resin Resin y rogen ceta Acro em Weight Cyanidedehyde Duolite A-7 M 80 66 70 Dowex-3 2l5 36 0 21 Amberlite I96 29 0 l6Permutit 218 30 0 ll de-Acidite components in comparison with the porousgranular Duolite A-7 resin salt. The porous, granular resinwas about 2/2 times more effective than the non-porous, spherical beaded resins inremoving hydrogen. cyanide. 5 The non-porous smooth resins wereineffective in *removing acetaldehyde. The non-porous resins were atbest, only one third as effective as the porous particulate resin inremoving acrolein from tobacco smoke.

EXAMPLE IV ln order to determine the effectiveness of the partiallyneutralized weakly basic anion exchange resins of the invention, theDuolite free base resins derived from the mixed chloride-sulfate saltsheretofore disclosed in Example I were thereafter neutralized withvarying quantities of acetic acid. The resulting filter material wasformed into a filter and tested according to the procedures of ExampleI. Each filter contained from 120 to 160 milligrams of resin. Theneutralization capacity of the Duolite A-7 free base resins is 5milliequivalents acetic acid per gram of resin. The effect of resinweight on the efficiency of the partially neutralized Duolite filters isalso tabulated.

Effect of Neutralization on Filtration Efficiencies NeutralizationFiltration Efficiencies (meq acid/g Hydrogen Acetalresin) Cyanide dehydeAcrolein 3O Duolite A-7 0.0 8! 3] 56 1.0 81 52 65 2.0 80 56 67 3.0 76 5566 5.0 80 66 70 Duolite A-2 0.0 82 49 52 1.0 80 63 66 2.0 80 67 73 3.080 77 78 5.0 80 79 72 The completely neutralized Duolite resins were 30to 35 percent more efficient for acetaldehyde and 15 to 20 percent moreefficient for acrolein than the free bases. Partial neutralization ofDuolite A-7 free base (1.0-3.0 meq/g) enhanced acetaldehyde and acroleinefficiencies by 20 to 25 percent and about 10 percent respectively.

The following resins were converted to their free base form andthereafter were partially neutralized with 2 milliequivalents of aceticacid. Each resin salt was intermixed with cellulose triacetate granulesto simulate resin dispersed on cellulose acetate tow. Each mixture wasformed into 13 mm filter beds and joined with an 8 mm cellulose acetatefilter. The dual filter was joined to a tobacco cylinder and testedaccordingto Example I.

Effect of Resin Weight on Efficiency Of Partially Neutralized DuoliteFilters Filtration Efficiencies Resin y roceta gen Weight (mgs)Cyadehyde Acrolein nide Duolite A-7 50 60 30 44 71 46 50 Duolite A-2 5062 37 44 I00 72 54 62 1. An improved cigarette filter comprising atubular filter outerwrap adapted to be affixed to a cylindricalsmokeable charge and an inner core filter contained within saidouterwrap, said inner core filter comprising 0 a plurality of porousgranular particles of a salt of a weakly basic anion exchange resin,said resin characterized by a surface area of from about 1 to 100 squaremeters per gram, a pore volume of from about 0.2 to

0.5 cubic centimeter per gram, and an average pore diameter of fromabout 0.01 to 1 micron, said salt being formed by the at least partialneutralization of the basic resin by a weak acid having a pK betweenabout 3.5 and 5.5.

2. The improved cigarette filter of claim 1 in which the acid employedfor neutralization has a pK between about 4 and 5.

3. The improved cigarette filter of claim 2 in which the acid isselected from the group consisting of acetic acid and glutamic acid.

4. The improved cigarette filter of claim 3 in which the weakly basicanion exchange resin is a phenolformaldehyde-polyamine terpolymer resin.

5. The improved cigarette filter of claim 1 wherein the weakly basicanion exchange resin contains at least about percent free primary aminogroups prior to reaction with the weak acid.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,828,800 Dated August 13, 1974 Inventofls) Elmer Francis Litzinger- Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the ABSTRACT, line 8; change v "0.1 to 1.0 "microns" to read Signed;4 d "sealed this 3rd day 0': December 1974.

(SEAL) Atteat:

McCOY M. 613mm. w c. MARSHALLDANN Attesting Officer Comis'sioner ofPatents uscoMM-nc c031 elven FORM PO-1050 (o-es) I v v u.sl oovnnuu'rnnmuc omci: nu o-Ju-au.

2. The improved cigarette filter of claim 1 in which the acid employedfor neutralization has a pKa between about 4 and
 5. 3. The improvedcigarette filter of claim 2 in which the acid is selected from the groupconsisting of acetic acid and glutamic acid.
 4. The improved cigarettefilter of claim 3 in which the weakly basic anion exchange resin is aphenolformaldehyde-polyamine terpolymer resin.
 5. The improved cigarettefilter of claim 1 wherein the weakly basic anion exchange resin containsat least about 30 percent free primary amino groups prior to reactionwith the weak acid.